Ink jet printers and plotters are well known. The print quality of these printers is dependent on the consistent, successful functioning of the ink jet print heads which are susceptible to clogging and failure over time. To overcome the problems with deterioration of ink jet print heads over time, it is necessary to periodically replace the print heads. Early solutions to this problem replaced only the print head, as shown, for example, in U.S. Pat. No. 4,074,284. More recently, disposable ink jet cartridges have been developed to solve this problem, as described, for example, in U.S. Pat. Nos. 4,500,895, 4,921,811 and 4,931,812.
Disposable ink jet cartridges of this type are designed to operate for a useful life such that the head elements will function a very high percentage of the time (e.g., 99% of the time) during the life of the disposable cartridge. To ensure that this demanding performance figure is maintained, conventional disposable ink jet cartridges have a predetermined amount of ink contained within the cartridge that is available to be dispensed through the print head. The maximum amount of ink that is contained in the disposable cartridge is a function of how much printing the print head elements can do before failing to function at the very high performance percentage. Once the predetermined amount of ink in the cartridge is used, the entire ink jet cartridge is discarded.
While the use of disposable cartridge has effectively guaranteed the print quality of ink jet printers at the failure rate dictated by the particular disposable cartridge, there are many print applications which could tolerate a higher failure rate in exchange for an extended period of operation of the ink jet print head. Unfortunately, when existing disposable ink jet cartridges run out of ink, the print head is still functioning adequately in the vast majority of cases. Discarding ink jet cartridges that still have adequately functioning print heads wastes resources. In addition, frequent replacement of ink jet cartridges is time and labor intensive for large print applications.
To solve this problem, several systems have been developed for refilling ink jet cartridges in order to prolong the useful life of the print heads. These systems include manual refilling of the ink jet cartridges, refilling the ink jet cartridges using a mechanical system of valves and pumps as described in U.S. Pat. No. 4,680,696, or periodically refilling the ink jet cartridges as part of a service-station type operation as described, for example in U.S. Pat. Nos. 4,959,667 and 5,136,305. Of the ink refill systems developed for ink jet printers that utilize disposable ink jet cartridges, the ink refill system with the most advantages has been a continuous ink refill system of the type described, for example, in U.S. Pat. Nos. 4,831,389 and 5,159,348.
In U.S. Pat. No. 4,831,389 issued to Chan, a continuous ink refill system delivers refill ink through supply tubes from a refillable off board ink supply to an ink jet print head positioned on the print carriage by capillary action created during an ink jet printing operation. In U.S. Pat. No. 5,159,348 issued to Dietl et al., a continuous ink refill system includes an ink reservoir mounted on the print carriage that supplies ink to the print head and is also connected by supply and return lines to an ink source that is remote from the print carriage. In Dietl et al., the supply line includes a restrictor that prevents a passive flow of ink greater than can be handled by the print head, and also includes a pump in the supply lines for priming the ink reservoir and the print head. Other examples of ink supply line arrangements for ink jet printers that do not use disposable ink jet cartridges are shown in U.S. Pat. Nos. 4,394,669, 4,475,116 and 4,590,495, as well as Japanese Abstracts Nos. 54-110682, 57-77546, 59-12027, 60-297219, and 61-63789.
As the speed at which the print carriages of these types of ink jet printers travels across the print bed has increased, and as the transverse distance of the print beds has also increased, a problem with the continuity and regularity of the flow of refill ink has been encountered with continuous ink refill systems. Intermittent surges or vacuums in the ink refill system may interfere with the delicate pressure balance required by the print head of the disposable ink jet cartridge. As a result, intermittent ink spotting or weeping, or missing or diminished ink pixels can occur. In addition, line movement or chatter in the ink supply lines can result in printing artifacts that degrade the overall print quality of the image.
In an effort to provide some support for ink supply lines, some ink jet printers that use fixed print heads, rather than disposable ink jet cartridges, have integrated or molded the ink supply lines inside a flexible conduit, as shown, for example, by U.S. Pat. Nos. 3,373,435, 5,025,270 and 5,043,746, as well as Japanese Abstract No. 62-335368. Although the increased stability of the flexibile conduit tends to decrease intermittent surges and vacuums in the ink refill system, in each of these references, the flexible conduit remains relatively free to move in an essentially undetermined path along the print bed as the print carriage traverses back and forth across the ink jet printer. In addition, the ink supply lines are permanently mounted to the flexible conduit and to the permanent print heads and therefore cannot be easily replaced.
While the use of continuous ink refill systems for disposable ink jet cartridges has increased the period of operation for ink jet printers using these cartridges, these types of continuous ink refill systems tend to decrease the overall print quality, particularly in larger and faster ink jet printers. Consequently, a disposable ink jet cartridge refill system that can increase the period of operation of the ink jet printer without significantly detracting from the overall print quality of the ink jet printer would be greatly appreciated.